This invention relates to the forming of a double seam between an end wall of a can and a body of a can.
Wall ironed can bodies commonly have a bottom wall and an integral side wall upstanding from the periphery of the bottom wall to terminate in a shoulder, a neck of reduced diameter, and an outwardly directed flange. It is usual for the majority of the side wall to be much thinner than the bottom wall. An annulus of arcuate cross-section connects the neck to the flange, and a typical radius of this arcuate annulus is 0.040". Wall ironed can bodies are usually coated internally after forming by sprayed lacquer. Can ends fitted to these wall ironed can bodies are stamped from precoated sheet metal such as tinplate, electrochrome coated steel (TFS), or aluminium alloy.
The can industry is asked to provide a variety of features on the sidewall of the can, such as texturing or can sidewall shaping, which can result in the can having a reduced axial strength. Due to this reduced axial strength, there can be problems encountered during the seaming of the can end onto the can, which is typically carried out using an axial load of approximately 650N.
Accordingly there is provided a method of making a double seam joining a can body to a can end, the can body having a side wall terminating in an outwardly directed flange, said method comprising the steps of:
a) supporting the can body, PA1 b) applying a can end to the flange of the can body, PA1 c) applying a load to force the can end and the can body one against the other, PA1 d) applying one or more operation seaming rolls to a peripheral curl of the can end to progressively form a double seam by a relative rolling motion, PA1 e) the flange angle (as hereinafter defined) is within the range 0 to -450.degree., and PA1 f) the load applied between the can end and the can body is 600N or less. PA1 a) forming an outwardly directed flange on the peripheral edge of the side wall of the can body, PA1 b) supporting the can body, PA1 c) applying a can end to the flange of the can body, PA1 d) applying a load to force the can end and the can body one against the other, PA1 e) applying one or more operation seaming rolls to a peripheral end of the can end to progressively form a double seam by a relative rolling motion, PA1 f) the flange angle angle (as hereinafter defined) is within the range 0 to -45.degree., and PA1 g) the load applied between the can end and the can body is 600N or less.
characterised in that,
Alternatively, there is provided a method of joining a can body to a can end with a double seam, the method comprising the steps of:
characterised in that:
The term "flange angle" is well known in the can making art and comprises the angle between the flange and the horizontal, assuming the can is standing upright. Typical conventional cans have a positive flange angle between 0 and 15.degree. (i.e. they are either horizontal or "point upwards" at an angle of up to 15.degree.). Cans with a negative flange angle (i.e. with a downwardly pointing flange) are known as having a "mushroom flange", and this is seen as being a flange defect produced by poor can making practices. U.S. Pat. No. 3,556,031 discloses a seaming technique which uses a downwardly directed can flange but this is a technique using a cam surface, rather than the double operation seaming roll technique which has become the industry's standard.